Is there some kind of trick involved? Here's how I would envision it working:

1) User tries submitting the form

2) Event.observe captures this and sends an AJAX request to a special validation URL (PHP using Codeigniter)

3) If no errors were returned, continue submitting the original form

4) If errors were found, cancel form submission and display

Mostly, I can't seem to get a separate AJAX validation request to work as the form continues submitting. I could use Event.stop(event), but have not found a way to re-start the process if no validation errors exist from the validation call. I'd post code, but I have about 15 examples of things I've tried and it would just clutter this question.

Any ideas? :-( I didn't think form validation would be this difficult.

Many thanks, - Matt